DxListBox<TData, TValue>.SetFilterCriteria(CriteriaOperator) Method

Applies a filter to List Box data.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v25.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public void SetFilterCriteria(
    CriteriaOperator criteria
)

Parameters

Name	Type	Description
criteria	CriteriaOperator	An object that specifies the filter expression.

Remarks

The Blazor List Box allows you to filter its data in code.

You can create a criteria operator object that specifies the filter expression and pass this object to the SetFilterCriteria method. For more information about criteria operators, see the following sections:

• Criteria Language Syntax
• Criteria Language Syntax - Custom Data Specifics

When a filter is applied, the List Box raises the FilterCriteriaChanged event.

You can call the ClearFilter() method to clear any previously applied filters and apply a new filter to list box data.

The following code creates a toolbar that allows you to apply filter criteria to List Box data and clear filter.

Razor

@using DevExpress.Data.Filtering
<DxToolbar ItemClick="@OnItemClick">
    <Items>
        <DxToolbarItem Name="_setFilterCriteria" Text="Set Filter Criteria" Tooltip="Set Filter Criteria" />
        <DxToolbarItem Name="_clearFilterCriteria" Text="Clear Filter Criteria" Tooltip="Clear Filter Criteria" />
    </Items>
</DxToolbar>
<br/>
<DxListBox @ref="@_listBox" TData=Person TValue=Person Data="Staff.DataSource"
            ShowCheckboxes="true"
            SelectionMode="@ListBoxSelectionMode.Multiple">
    <Columns>
        <DxListEditorColumn FieldName="FirstName"></DxListEditorColumn>
        <DxListEditorColumn FieldName="LastName"></DxListEditorColumn>
        <DxListEditorColumn FieldName="Department"></DxListEditorColumn>
        <DxListEditorColumn FieldName="Salary"></DxListEditorColumn>
    </Columns>
</DxListBox>
<p class="cw-480 mt-3">
    Filter Criteria: <b>@_listBox?.GetFilterCriteria()?.ToString()</b>
</p>

@code {
    IListBox<Person, Person> _listBox;
    void OnItemClick(ToolbarItemClickEventArgs e) {
        switch(e.ItemName) {
            case "_setFilterCriteria":
                _listBox.SetFilterCriteria(new BinaryOperator(nameof(Person.Salary), 2000, BinaryOperatorType.Greater));
                break;
            case "_clearFilterCriteria":
                _listBox.ClearFilter();
                break;
        }
    }
}

StaffData

namespace StaffData {
    public static class Staff {
        private static readonly Lazy<List<Person>> dataSource = new Lazy<List<Person>>(() =>
        {
            Random rnd = new Random();
            var dataSource = new List<Person>() {
                new Person() { Id = 0 , FirstName = "John John", LastName = "Heart", Department = Department.Electronics, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 1 , FirstName = "Samantha", LastName = "Bright", Department = Department.Motors, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 2 , FirstName = "Arthur", LastName = "Miller", Department = Department.Software, Salary = GetRandomSalary(rnd)   },
                new Person() { Id = 3 , FirstName = "Robert", LastName = "Reagan", Department = Department.Electronics, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 4 , FirstName = "Greta", LastName = "Sims", Department = Department.Motors, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 5 , FirstName = "Brett", LastName = "Wade", Department = Department.Software, Salary = GetRandomSalary(rnd)   },
                new Person() { Id = 6 , FirstName = "Sandra", LastName = "Johnson", Department = Department.Electronics, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 7 , FirstName = "Edward", LastName = "+Holmes", Department = Department.Motors, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 8 , FirstName = "Barbara", LastName = "Banks", Department = Department.Software, Salary = GetRandomSalary(rnd)  },
                new Person() { Id = 9 , FirstName = "Kevin", LastName = "Carter", Department = Department.Electronics, Salary = GetRandomSalary(rnd) },
                new Person() { Id = 10, FirstName = "Cynthia", LastName = "Stanwick", Department = Department.Motors, Salary = GetRandomSalary(rnd)   },
                new Person() { Id = 11, FirstName = "Sam", LastName = "Hill", Department = Department.Electronics, Salary = GetRandomSalary(rnd)   },
            };
            return dataSource;
        });
        public static List<Person> DataSource { get { return dataSource.Value; } }
    }

    public class Person {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public Department Department { get; set; }
        public string Text => $"{FirstName} {LastName} ({Department} Dept.)";
        public decimal Salary { get; set; }
        public DateTime BirthDate { get; set; }
        public override bool Equals(object obj) {
            if (obj is Person typedObj) {
                return (this.Id == typedObj.Id) && (this.FirstName == typedObj.FirstName) && (this.LastName == typedObj.LastName)
                && (this.Department == typedObj.Department);
            }
            return base.Equals(obj);
        }
    }

    static decimal GetRandomSalary(Random rnd) {
        return rnd.Next(1000, 3000);
    }

    public enum Department { Motors, Electronics, Software }
}

Run Demo: List Box - Filter Criteria

Criteria Language Syntax - Custom Data Specifics

If you bind the List Box to custom data, you can use the following criteria operators.

Binary Operator

The BinaryOperator criteria operator allows you to compare operand property with operand value. You can use the following operator types for comparison: Equal, NotEqual, Greater, GreaterOrEqual, Less, and LessOrEqual.

var criteria = new BinaryOperator("UnitPrice", 20, BinaryOperatorType.Less);

Unary Operator

The UnaryOperator criteria operator allows you to apply Not or IsNull operation to an expression.

var criteria = new UnaryOperator(UnaryOperatorType.Not, new UnaryOperator(UnaryOperatorType.IsNull, "Region"));

Function Operator

The FunctionOperator criteria operator allows you to create a complex filter criteria with the following operator types:

• IsNull and IsNullOrEmpty operands indicate whether a specified operand is a null reference or an empty string.
• InRange operand determines whether a property value is contained in the specified range.
• StartsWith, EndsWith, and Contains operands allow you to compare a property with a string value.

var criteria = new FunctionOperator(FunctionOperatorType.StartsWith, new OperandProperty("ShipCountry"), "it");

Group Operator

The GroupOperator criteria operator allows you to create a logical expression that groups two or more operands with a logical AND or OR.

var criteria = new GroupOperator(GroupOperatorType.And,
        new BinaryOperator("UnitPrice", 20, BinaryOperatorType.Less),
        new FunctionOperator(FunctionOperatorType.StartsWith, new OperandProperty("ShipCountry"), "it")

Between Operator

The BetweenOperator criteria operator allows you to determine whether a criteria expression lies between the specified range of values.

var criteria = new BetweenOperator("UnitPrice", 15, 20);

In Operator

The InOperator criteria operator allows you to determine whether a property value matches any value in a specified list.

var criteria = new InOperator("ShipCountry", new string[] { "Italy", "German", "France" });

Implements

SetFilterCriteria(CriteriaOperator)